The present invention relates to electrical machines such as generators and, more particularly, to a stator assembly in which the windings are laid into stator slots defined about an inner core and thereafter an outer core is installed to complete the assembly.
In electrical machines, armature windings must be assembled parallel to the axis of the stator.
Conventional generator windings are composed of bars that are brazed at the end windings to create coils. These pre-formed bars are inserted through the bore of the stator and placed into rectangular slots in a core composed of laminations. As such, the conventional generator windings do not need significant machinery to install. If these windings are defined by cables, the cable must be formed into a straight section and end arms. This requires significant forces to be applied to shape the cable which will in general require a large mechanism, larger than could be conveniently passed through the bore of a conventional machine.
From about 1959 through 1965, GE Power Systems Lynn Works developed a cable wound generator. This generator used a winding approach where each phase belt of the winding was drawn through a core with discreet holes for the cable. This required all of the cable to be drawn through most of the core.
In 1999, ABB released their Powerformer, a high-voltage, cable wound generator that uses a similar approach to the Lynn system. The major differences include the fact that the core has a slot with a semi-circular indentations to hold the cables.
It would be desirable to reduce winding time by providing greater access to the machine during the winding application process. Even if the windings are defined by bars or full coils, it would be desirable to provide greater access to the teeth and, more particularly, the slots therebetween for assembly.
The invention provides an inner core for electrical machines such as generators for installing windings from the convex surface of the inner core radially outwardly rather than inserting cables or bars through the bore of an assembled stator and placing them into rectangular slots in a core composed of laminations. More specifically, to provide more access to the machine during the assembly process and to minimize winding time, an inner core is provided for receiving teeth, each of which are defined by a plurality of laminations and about which the windings are respectively disposed. An outer core is applied to the assembly of the inner core and teeth with windings applied thereto to complete the stator assembly. Because the outer core is applied after winding has been completed, full access to the slots between the teeth and the windings disposed therewithin is provided during the assembly process.